[PATCH v3 13/13] mm/huge_memory: add and use has_deposited_pgtable()

Lorenzo Stoakes (Oracle)
2026-03-20T18:08:12Z

Rather than thread has_deposited through zap_huge_pmd(), make things
clearer by adding has_deposited_pgtable() with comments describing why in
each case.

Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
---
mm/huge_memory.c | 33 ++++++++++++++++++++++++---------
1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 5831966391bd..610a6184e92c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2326,8 +2326,7 @@ static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
}

static void zap_huge_pmd_folio(struct mm_struct *mm, struct vm_area_struct *vma,
- pmd_t pmdval, struct folio *folio, bool is_present,
- bool *has_deposit)
+ pmd_t pmdval, struct folio *folio, bool is_present)
{
const bool is_device_private = folio_is_device_private(folio);

@@ -2336,7 +2335,6 @@ static void zap_huge_pmd_folio(struct mm_struct *mm, struct vm_area_struct *vma,
folio_remove_rmap_pmd(folio, &folio->page, vma);

if (folio_test_anon(folio)) {
- *has_deposit = true;
add_mm_counter(mm, MM_ANONPAGES, -HPAGE_PMD_NR);
} else {
add_mm_counter(mm, mm_counter_file(folio),
@@ -2363,6 +2361,27 @@ static struct folio *normal_or_softleaf_folio_pmd(struct vm_area_struct *vma,
return pmd_to_softleaf_folio(pmdval);
}

+static bool has_deposited_pgtable(struct vm_area_struct *vma, pmd_t pmdval,
+ struct folio *folio)
+{
+ /* Some architectures require unconditional depositing. */
+ if (arch_needs_pgtable_deposit())
+ return true;
+
+ /*
+ * Huge zero always deposited except for DAX which handles itself, see
+ * set_huge_zero_folio().
+ */
+ if (is_huge_zero_pmd(pmdval))
+ return !vma_is_dax(vma);
+
+ /*
+ * Otherwise, only anonymous folios are deposited, see
+ * __do_huge_pmd_anonymous_page().
+ */
+ return folio && folio_test_anon(folio);
+}
+
/**
* zap_huge_pmd - Zap a huge THP which is of PMD size.
* @tlb: The MMU gather TLB state associated with the operation.
@@ -2375,7 +2394,6 @@ static struct folio *normal_or_softleaf_folio_pmd(struct vm_area_struct *vma,
bool zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
pmd_t *pmd, unsigned long addr)
{
- bool has_deposit = arch_needs_pgtable_deposit();
struct mm_struct *mm = tlb->mm;
struct folio *folio = NULL;
bool is_present = false;
@@ -2401,12 +2419,9 @@ bool zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
is_present = pmd_present(orig_pmd);
folio = normal_or_softleaf_folio_pmd(vma, addr, orig_pmd, is_present);
if (folio)
- zap_huge_pmd_folio(mm, vma, orig_pmd, folio, is_present,
- &has_deposit);
- else if (is_huge_zero_pmd(orig_pmd))
- has_deposit = !vma_is_dax(vma);
+ zap_huge_pmd_folio(mm, vma, orig_pmd, folio, is_present);

- if (has_deposit)
+ if (has_deposited_pgtable(vma, orig_pmd, folio))
zap_deposited_table(mm, pmd);

spin_unlock(ptl);
--
2.53.0